1. Field of the Invention
The present invention relates to a process involving the catalytic carbonylation of an allylic butenol or a butenyl ester of a carboxylic acid in a carboxylic acid solvent to produce a beta-gamma unsaturated carboxylic acid anhydride. More specifically but not by way of limitation, the invention relates to the use of a rhodium-containing catalyst promoted by a metal iodide salt under anhydrous conditions for the carbonylation of crotyl acetate, 3-acetoxybutene-1 and mixtures thereof to produce 3-pentenoic acid anhydride.
2. Description of Related Art
The use of rhodium-containing catalyst with various types of co-catalysts and promoters for the carbonylation of a variety of saturated and unsaturated organic compounds is generally known. For example, U.S. Pat. No. 4,603,020 claims a process for the carbonylation of O-acetyl compounds, such as acetic anhydride, at 130 to 250.degree. C. using a rhodium catalyst and an aluminum accelerator. U.S. Pat. No. 4,625,058 teaches a similar process but uses boron, bismuth or tertiary amide compounds as accelerators. U.S. Pat. No. 4,642,370 discloses a process for the carbonylation of hydrocarbyl halides which uses a boron, silicon, aluminum, or zirconium accelerator. U.S. Pat. No. 4,563,309 claims a process for the production of carboxylic acid anhydride of the formula RC(O)O(O)CCH.sub.3 by reaction of a methyl carboxylate ester of formula RC(O)OCH.sub.3 with carbon monoxide in the presence of a rhodium catalyst and a phosphorous-containing ligand.
European patent application 0 428 979 A2 discloses the carbonylation of allylic butenols and butenol esters using a rhodium catalysts and a hydrogen bromide or hydrogen iodide promoter under anhydrous conditions for the production of 3-pentenoic acid. However, the use of the hydrogen iodide promoter results in a back reaction producing butadiene and a carboxylic acid. The present invention alleviates this problem and as such is viewed as an improvement relative to this disclosure.